Hi Matt,
First, awesome picture with Mickey covering his eyes. Love it!
Second, yes, renting a car is probably the easiest and least expensive thing, although it's not easy to find a rental car office near the port. My sister had to cab it to the airport to get her car.
BUT, if you rent with National or Alamo, you can rent it one-way and drop it off at the Car Care Center next to the Magic Kingdom and then just use Disney transportation to get around the parks and the Magical Express back to the airport.